A low molecular weight fraction was obtained from a mass polymerised PVC resin by using diethyl ether Soxhlet extraction followed by either preparative gel filtration or solvent fractionation. A gas chromatography - mass spectroscopy (GC-MS) analysis of this fraction revealed that, in addition to vinyl chloride (VC) oligomers, it contained a large number of other compounds, in particular a large concentration of phthalates. By using adsorption liquid chromatography it was possible to remove the phthalates, along with other contaminants having a similar or greater polarity, from the low molecular weight PVC fraction.

Resins containing dibenzo-18-crown-6 (phiDB18C6) as anchor groups have been prepared according to the procedure suggested by Blasius and the total capacity, CT, determined by micro analysis. The effective capacity, CE, of phiDB18C6 towards the alkali-metal salts using water as reaction media was obtained from saturation experiments. The electrolyte concentration dependence of the distribution ratio of 1:1 electrolytes between phiDB18C6 and water at 298K was studied and the results used to determine the concentration range at which a maximum separation factor between two ions could be achieved. The rational equilibrium constant, log K'ex, corrected for activity in the solution phase and the derived apparent free energy change, DeltaG'ex for the process taking place when phiDB18G6 is equilibrated with an aqueous or non-aqueous solutions (s) of the different M+A- electrolytes as represented by are calculated. The results obtained clearly reflect the influence of the anions on the extraction of cations by the resin containing the macrocyclic ligand. For aqueous solutions of electrolytes containing a common cation and different anions the selectivity found is in the order Pi→SCN→I→Br→C1-. An enhancement of selectivity by a factor of 1.55x104, 8.91x103, 2.09x103 and 1.55x103 is found for the picrate salts relative to the chloride, bromide, iodide and thiocyanate, respectively. The heats associated with the interaction of phiDB18C6 and 1:1 electrolytes in aqueous solutions were measured calorimetrically at 298K and the apparent enthalpy change evaluated. Combination of the free energy and enthalpy changes yield the corresponding entropy changes. The contribution of the enthalpy and entropy terms to the free energy suggests that the process of extraction of 1:1 electrolytes from the aqueous I s solution to the resin phase is enthalpically controlled. An interesting relationship is obtained when values for the effective capacity of the resin towards the different 1:1 electrolytes are plotted against the apparent enthalpies(DeltaH'ex) obtained for the different electrolytes in water. Distribution data for the 1:1 electrolytes and phiDB18C6 were obtained in solvents such as N,N-dimethylformamide (DMF), propylene carbonate (PC), acetonitrile, (AN), methanol (MeOH) and water (H2O), in an attempt to evaluate the reaction media effects on the extraction of 1:1 electrolytes by these resins. Distribution ratios decrease in the order AN→PC→MeOH→DMF→H2O. Interaction between organic molecules in aqueous solutions (urea, thiourea, and phenol) and phiDB18C6 were also studied. Effective capacity measurements as determined by saturation experiments at 298K using thiourea and phenol indicate that the 1:1 organic molecule crown ether ratio obtained for the former compound is altered to a 4:1 ratio in the case of phenol. A possible mechanism based on hydrogen bond formation in the resin phase is suggested.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Increasing prevalence of dental erosion has been observed in many countries, in both children and adults. This condition is often associated with softening of the dental surface by acid exposure, which may lead to severe and irreversible damage. The use of fluoride, pit and fissure sealants, dental adhesives and more recently a resin infiltrant has been suggested to manage dental erosion. Objective: To compare the protective effect of a resin infiltrant and other resin-based materials against dental erosion/toothbrushing abrasion in vitro. Materials and methods: Bovine enamel and dentin slabs were prepared, embedded, flattened and polished. Dental erosion lesions were created using 0.01 M of hydrochloric acid (pH 2.3 for 30 sec) and treated with resin-based materials (HS: Helioseal pit and fissure sealant; SP: Seal and Protect dentin 78 sealant, and IC: Icon resin infiltrant) or fluoride varnish (FV: Duraphat). A no-treatment group represented the negative control (C). The specimens were subjected to an erosion-abrasion cycling model for a total of 10 days. Each cycling day consisted of 2 min immersion in 0.01M HCl, at room temperature, for 4 times; and toothbrushing with either of the abrasive suspensions (low and high, as previously determined by the radioactive dentin abrasivity method). Enamel and dentin surfaces were scanned at baseline, after treatment, at 5 days and at 10 days using an optical profilometer. Surface change (loss/gain) was determined by subtracting the treated area from the reference (protected) areas. Significance level of 5% was adopted for the statistical analysis. Results: No differences were found among groups at baseline, regardless of substrate. After treatment, surface deposition was found for all test groups except for IC, which did not differ from C. For enamel, at day 5, FV, HS and SP had less surface loss than C and IC (p<0.0008), which did not differ from each other (p=1.00). At day 10, similar trend was observed except for FV, which showed surface loss similar to C, when brushed with high abrasive suspension. High abrasive caused more surface loss than low abrasive only for C at day 5 (p=0.0117) and 10 (p=0.0162). For dentin, at day 5, FV, HS and SP had less surface loss than C and IC (p≤0.0001), which did not differ from each other (p=1.00). At day 10, HS and SP had less surface loss than C, IC, and FV (p<0.0001), and FV had less surface loss than C for low abrasive (p=0.0009). Overall, high abrasive had significantly more surface loss than low abrasive at 10 days (p=0.0280). Conclusion: HS was the most effective material protecting enamel and dentin from erosion-abrasion, followed by SP. FV offered limited protection, while no benefit was observed for resin infitrant IC.

Urea formaldehyde (UF) resins are widely used as adhesives for wood-based composites. These thermosetting polymers have advantages of relative low price, fast curing speed, and relative good bonding performance. However, UF resin bonded composites are designed for interior applications due to its weak water resistance. Moreover, traditional prevalent ways for recycling wood-based composites face problems caused by UF resins. In this project, the reuse of cured UF resins was systematically studied. The verification and characterization of crystalline structures in cured UF resins were conducted. The results showed that the crystalline regions were accounted for nearly 14.48% in a typical 1.2 formaldehyde to urea (F/U) molar ratio UF resin. The details of the resin crystalline regions, such as grain sizes and interplanar spacing (d-spacing), were characterized. The crystalline structures, nevertheless, did not affect the UF resin hydrothermal hydrolysis in this study. The reuse of cured UF resin was started with a hydrothermal hydrolysis. Under 140 °C and 2 h of hydrothermal process, 20 mL of 30 w.t. % formaldehyde water solution was able to depolymerize up to 1.7 g of cured UF resin. The hydrolyzed formaldehyde solutions were directly used as normal formaldehyde solutions for UF resin synthesis. The synthesized resin (named as UUF resin) contained about 6 w.t. % of cured UF resin and presented similar chemical structures and bonding performance as normal UF resins. Hybrid resins made of UUF resin and polymeric 4-4 diphenyl methane diisocyanate (pMDI) were prepared. The pMDI was found evenly dispersed in the hybrid resins by using acetone as its solvent. These hybrid resins resulted in faster curing and stronger bonding performance than pure UUF resins. Furthermore, the hybrid resin was used in a new bonding design, which used southern pine wood radial section features. This design generated finger joint like bonding interfaces by hot pressing two resin coated wood radial sections. The bonding strength and bond line stability were enhanced by this design.

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